<!DOCTYPE html>
<html class="reftest-wait">
   <head>
     <title>mo@accent</title>
     <meta charset="utf-8"/>
     <script type="text/javascript">
       function doTest() {
         document.getElementById('mathOperator').setAttribute('accent', 'true');
         document.documentElement.removeAttribute("class");
       }
       window.addEventListener("MozReftestInvalidate",doTest, false);
     </script>
    </head>
    <body>
     <math>
      <munderover><mtext>X</mtext><mo id="mathOperator">O</mo><mo>O</mo></munderover>
     </math>
    </body>
</html>